This invention relates in general to coking and in particular to a new and useful method and apparatus for cooling bulk material such as coke.
In prior art dry coke cooling plants (for example according to German AS No. 10 71657), the hot coke produced in a coke oven battery is cooled by directing an inert cooling gas through the hot coke layer. It is further known (from Swiss Pat. No. 101,570) to circulate the cooling gas and re-cool it in a heat exchanger which is designed as a boiler. In addition, a blower for circulating the cooling gas, and a preliminary dust separator and a fine dust separator are provided in the cooling gas circuit.
To obtain the desired steam production in the waste heat boiler and then a uniform generation of energy, a continuous operation of the coke cooling chambers is needed, i.e. only small variation in the heat amount removed from, and in the temperature of, the hot coke in the cooling chamber can be tolerated. This requires special measures.
According to German AS No. 26 18 654, variations in the heat amount delivery caused by the intermittent bulk material supply are compensated for, and the plant conduits, particularly the boiler tubes, are prevented from overheating by branching off a controllable partial stream of the cooling gas before it enters the vertical chamber, and reuniting it with the heated cooling gas stream ahead of the entrance into the re-cooling heat exchanger. The equipment for carrying out the method comprises a bypass which is parallel to the cooling chamber and in which the partial stream of cooling gas is branched off after the circulating blower and is directed through a mixer for controlling the inlet temperature of the hot cooling gas, into the heat exchanger. In the head zone of the cooling chamber, the hot cooling gas is taken off about at the level of the outlet of the charging lock. By directing a variable amount of gas into the cooling chamber and introducing the balance through the bypass into the outlet line for the hot cooling gas, conditions are to be created for keeping the temperature of the cooling gas at the entrance into the recooling heat exchanger at about 550.degree. C. to 650.degree. C. It must be taken into account in this connection that only a partial gas stream is available for cooling the charged bulk material, while the gas recycling equipment, particularly the recooling heat exchanger, the dust separator, the circulation blower, and the gas lines must be dimensioned for the entire gas amount.
In another method, disclosed in German Pat. No. 1,471,589, to obtain a sufficiently uniform rate of heat removal from the hot coke, a cooling chamber of refractory masonry with two operating zones is provided and the hot coke is kept ready in the antechamber section through which the cooling gas does not pass, and is cooled only after sinking into the lower section of the cooling chamber, by a countercurrently flowing gas stream, to the discharge lock exit temperature. The antechamber section is effective as a heat bank and temperature buffer. What is disadvantageous is that the large volume cooling chamber has a very complicated structure. An inner abrasion layer of refractory material is followed by layers of thermal insulation and backfilling inside a steel shell. In the interior of the masonry, passages and a ring conduit for evacuating the hot cooling gas are provided. This results in high capital investment and high operating costs.